1. Field of the Invention
The present invention relates to an improvement in a conveyer magazine-type empty bag supplying apparatus used to supply empty bags to a bag filling packaging machine.
2. Description of the Related Art
Japanese Patent Application Laid-Open (Kokai) No. 2003-137219 discloses a conveyer magazine-type empty bag supplying apparatus used to supply empty bags to an intermittently rotating rotary-type bag filling packaging machine. This conveyer magazine-type empty bag supplying apparatus includes: a belt conveyer for conveying a set of empty bags stacked with a displacement in the fore-and-aft direction of (or in a direction parallel to) the conveying direction of the belt conveyor such that the mouths of the bags face forward and upper empty bags are shifted forward, a fast-feed belt (an empty bag separating means) provided above the belt conveyer, ratchet wheels provided on a forward side of the fast-feed belt, a positioning stopper provided near the forward end of the belt conveyer, and empty bag suction members provided between the ratchet wheels and the positioning stopper.
In the above structure, the fast-feed belt separates the topmost empty bag from the set of the empty bags on the belt conveyer and feeds it forward. The ratchet wheels, which have a plurality of flexible radially-extending pawl elements (projections) arranged around them, are connected to a drive source and rotate, while moving up and down between its lower delivery position and its upper retracted position, such that, in the delivery position, they come in contact with the empty bag fed by the fast-feed belt and feed it farther forward, causing the bag to come into touch with the positioning stopper. The positioning stopper, which is provided near the forward end of the belt conveyer, is used for positioning the empty bags supplied by the ratchet wheels. The empty bag suction members are moved up and down between its lower suction position, in which they adhere to the upper surface of an empty bag positioned by the positioning stopper, and its upper pickup position.
In addition, a chuck used for transporting empty bags is provided between the conveyer magazine-type empty bag supplying apparatus and the intermittently rotating rotary-type bag filling packaging machine. When the empty bag suction members arrive at the pickup position, the upper edge portion of the adhered empty bag is gripped by this chuck, and the empty bag is subsequently transported by the chuck and transferred to the grippers of the intermittently rotating rotary-type bag filling packaging machine.
Japanese Patent No. 3,639,199 discloses another type of conveyer magazine-type empty bag supplying apparatus used to supply empty bags to a bag filling packaging machine. The basic construction of this conveyer magazine-type empty bag supplying apparatus is substantially the same as that of Japanese Patent Application Laid-Open (Kokai) No. 2003-137219 in which an empty bag fed forward by the fast-feed belt is fed farther forward and caused to come into touch with the positioning stopper by ratchet wheels provided behind the empty bag suction members; however, in the apparatus of Japanese Patent No. 3,639,199, rotating rollers are provided, instead of ratchet wheels, so that the rotating rollers are moved up and down in an oscillating manner and in equilibrium with a balancer in a position that is substantially aligned with the empty bag suction members.
The conveyer magazine-type empty bag supplying apparatus described in Japanese Patent Application Laid-Open (Kokai) No. 2003-137219 has several problems as noted below:                (1) Since the ratchet wheels are provided between the fast-feed belt and the empty bag suction members, the gap between the ratchet wheels and the positioning stopper is relatively wide. For this reason, an empty bag fed by the ratchet wheels is, after having come into touch with the positioning stopper, warped upward or undergoes convex deformation, resulting in such problems as positioning errors of the empty bag and pickup errors that would occur when the empty bag suction members pickup the empty bag. This will be described below with reference to FIGS. 4A and 4B. In FIGS. 4A and 4B, the reference numeral 1 designates an empty bag, 2 a ratchet wheel, 3 a belt conveyer, 4 a positioning stopper, 5 a position-detecting sensor, 6 an empty bag suction member, 7 a belt conveyer frame, and 8 a lateral guide for the belt conveyer.        (1) When an empty bag 1 is fed forward by the fast-feed belt (not shown), the ratchet wheels 2, which rotate in the direction of the curved arrow, descend from the retracted position indicated by the two-dot chain line to the delivery position indicated by the solid line and come in contact with the upper surface of the empty bag 1 on the belt conveyer 3, and then the empty bag 1 is fed further forward on the belt conveyer 3 by the ratchet wheels 2, and its front end (mouth edge) comes into touch with the positioning stopper 4, and then the bag is properly positioned by the positioning stopper 4. The position-detecting sensor 5 detects the bag 1 thus positioned. After detection by the position-detecting sensor 5, the ratchet wheels 2 stay in the delivery position for some time in order to permit reliable determination of the position of the bag 1 and continue feeding of the bag 1. Subsequently, the ratchet wheels are raised to the retracted position. At that time, as a result of overfeeding by the ratchet wheels 2, the front part of the empty bag may bend upward (as shown in FIG. 4A) or undergo convex deformation (as shown in FIG. 4 B), which leads to positioning errors and pickup errors when the empty bag suction members 6 pick up the bag. This problem is especially pronounced when the empty bag 1 is relatively soft.        (2) In the conveyer magazine-type empty bag supplying apparatus, the delivery position of the ratchet wheels 2 is mechanically set in advance. For this reason, if the supplied empty bag 1 is one made of relatively thick material, or if there is a pile of a plurality of empty bags 1 fed by the fast-feed belt, the force of contact of the ratchet wheels 2 applied on the empty bag 1 (the degree of bending of the flexible pawls) increases, which leads to overfeeding and causes the above-described problem (1) to occur in a pronounced manner.        (3) If the location of the positioning stopper 4 is made freely adjustable in the fore-and-aft direction, then changing its location makes it possible to adjust the gap between the front end of the empty bag 1 and the suction position of the empty bag suction members 6 and to change the vertical position of the empty bag 1 supplied to the grippers of the packaging machine (and thus change the sealing position and the vertical width of the seal). In this configuration, when the position of the positioning stopper 4 is moved forward, the gap between the positioning stopper 4 and the ratchet wheels 2 is widened, and this causes the above-described problem (1) to occur in a pronounced manner as well.        (4) The timing of the descend of the ratchet wheels 2 to the delivery position is set to occur after the fast-feed belt separates the topmost empty bag 1 from the set of empty bags on the belt conveyer 3 and feeds it forward, and when the ratchet wheels 2 descend to the delivery position, the ratchet wheels 2 come into contact with the upper surface of the supplied empty bag 1. For this reason, if the front portion of the empty bag 1 is already warped, its warp cannot be rectified, and it is difficult to properly position the empty bag 1.        (5) On the other hand, it is believed that in the conveyer magazine-type empty bag supplying apparatus described in Japanese Patent No. 3,639,199, the above-described problems (1)-(4) are less likely to occur than in the apparatus of Japanese Patent Application Laid-Open (Kokai) No. 2003-137219 because the rotating rollers, which are believed to correspond to the ratchet wheels 2 of Japanese Patent Application Laid-Open (Kokai) No. 2003-137219, are disposed in positions where they are substantially aligned with the empty bag suction members; and as a result, the gap between the rotating rollers and the positioning stopper is reduced and, in addition, the rotating rollers are almost always in the lower position in equilibrium with a balancer and the empty bags fed by the fast-feed belt are pressed down by the rotating rollers. Since, however, the rotating rollers are in contact with the surface of the empty bag while in equilibrium with the balancer and are constantly pushing the empty bag against the positioning stopper, it is undeniable that the warping and convex deformation described in (1) above would occur in the empty bag at that time.                    In addition, in this conveyer magazine-type empty bag supplying apparatus of Japanese Patent No. 3,639,199, when the empty bag suction members holding an empty bag are raised, there is a risk that the empty bag may come in contact with the rotating rollers and lift the rollers up; and when this happens the empty bag is separated from the empty bag suction members or is caused to position changes. Due to the positional relationship between the rotating rollers and the empty bag suction members, it is believed that as long as the rotating rollers do not deviate from the trajectory of an empty bag, an empty bag cannot be brought to the pickup position above the belt conveyer. However, there are questions about whether it is actually possible for an empty bag held by the empty bag suction members to lift the rotating rollers up. Even if it is possible and lifting of rotating rollers occurs whenever one empty bag is supplied, production efficiency (supply rate) would be extremely low and unstable.                        